LITTLE ROCK (AP) — The Little Rock airport was closed for about an hour and a half Thursday as authorities investigated a suspicious suitcase.

A bomb-sniffing dog alerted on the bag, which turned out not to contain any explosive material, but the investigation led officials to halt departing flights briefly at the Bill and Hillary Clinton National Airport, spokesman Shane Carter said.

Four flights were canceled and an evacuation forced hundreds of people from the airport as passengers waiting for departing flights were escorted out, Carter said. Passengers on arriving flights were also escorted away from the terminal while authorities investigated the bag, Carter said.

The bag had apparently been at the airport since Wednesday night, Little Rock Fire Department Capt. Jason Weaver said.

A bomb-sniffing dog alerted on it during a sweep Thursday afternoon, prompting authorities to X-ray the bag, which was in a luggage-holding area, Weaver said. It contained personal items, but Weaver said investigators planned to swab it to figure out what the dog was reacting to.

“It may have been exposed to something in the past,” Weaver said, adding that no one was in danger Thursday.